Table 1.

Historical Period and Age of Diagnosis by Subspecialists

Period	N	Median Age of Diagnosis (y)	Mean Rank	Significantly different from periods:
A: 1983a – 1984	13	6.33	645.8	F*, G**, H**, I**
B: 1985b – 1987	50	6.17	591.0	D**, F**, G***, H***, I***
C: 1988c – 1994	84	3.08	494.6	G**, H***, I**
D: 1995d – 1998	64	2.91	410.3	B**
E: 1999e – 2000	88	3.08	471.3	H**
F: 2001f	39	2.50	376.7	A*, B**
G: 2002g – 2005	196	2.50	377.1	A**, B***, C**
H: 2006h – 2009	194	2.41	355.9	A**, B***, C***, E**
I: 2010i – 2014	96	2.54	364.8	A**, B***, C**
Total	824	2.75

Periods divided based on:

^a1983, first description of the disorder in English;

^b1985, first diagnostic criteria for diagnosis;

^c1988, update to diagnostic criteria;

^d1995, atypical RTT criteria;

^e1999, association between MECP2 mutations and RTT;

^f2001, clinical availability of MECP2 testing and AAP developmental screening recommendations;

^g2002, update to diagnostic criteria;

^h2006, AAP routine screening algorithm for developmental disorders;

ⁱ2010, update to diagnostic criteria.

^*p - value <.05,

^**p - value <.01,

^***p - value <.001